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From: eachus@spectre.mitre.org (Robert I. Eachus)
Subject: Re: Fortran or Ada?
Date: 1998/09/23
Message-ID: <EACHUS.98Sep23153612@spectre.mitre.org>#1/1
X-Deja-AN: 394101099
References: <36068E73.F0398C54@meca.polymtl.ca>
 <slrn70dv6k.2qp.gisle@krake.ii.uib.no> <6uan3f$7qe$1@nnrp1.dejanews.com>
Organization: The Mitre Corp., Bedford, MA.
Newsgroups: comp.lang.fortran,comp.lang.ada
Date: 1998-09-23T00:00:00+00:00
List-Id: <comp.lang.ada>

In article <6uan3f$7qe$1@nnrp1.dejanews.com> bglbv@my-dejanews.com writes:

 > Also remember that the design and testing methodology often counts for more
 > than the language itself. Ariane 501 was lost due to a bug in Ada code.
 > (My understanding is that it was an error in the specification; that the
 > code happened to be written in Ada was not particularly significant.)

   Actually the fact that it was written in Ada did help find the
potential problem.  Unfortunately, when it was reviewed in a Ariane 4
context, the potential problem was found, but it was not fixed since
it could "never happen."  Physical constraints prevented the problem
from ever occuring in an Ariane 4.  The problem was in reusing the
guidance software in the Ariane 5 without changes or review.  This can
be seen in the fact that once the bug occurred, the engines deflected
enough to cause the stack to break apart, just like a falling chimney.

   So the real problem was that the Ariane 5 was flying with software
whose built in safety limits were set for the Ariane 4.  The
particular case that caught them was just the first to materialize.

   Remember this the next time someone tells you how wonderful
software reuse is.
--

					Robert I. Eachus

with Standard_Disclaimer;
use  Standard_Disclaimer;
function Message (Text: in Clever_Ideas) return Better_Ideas is...